1. The
Internal
Environment overview

2. by the end of the lesson you will be able to
Learning objectives:
by the end of the lesson you will be able to
Explain the processes that take place in the body to maintain a constant temperature.
Explain the importance of keeping temperature at 37oC to allow the enzymes in the body to achieve there optimum rate of reaction.
Describe how water and ions are lost through the skin when sweating.

3. bloodstream brain glands hormones pituitary
Starter
Name______________ Class___________ Date __________
_______________ are chemical messengers. They are secreted by _______________ found around the body. They travel through the _______________ to organs where they control important processes. The system of glands and hormones is called the endocrine system. It is controlled by the _______________ which sends hormones to the _______________ gland to control other organs. Organs controlled by hormones include the testes and ovaries.
bloodstream brain glands hormones pituitary

4. Feeling the heat When you feel too hot, how does your body react?
You sweat, which helps to cool you down.
Another cooling effect is that blood vessels in the skin expand.
This means that more blood gets near the surface of the skin, which is why some people go red when they are too hot!
The expansion of blood vessels uses some of the energy released by respiration.
How do blood vessels use this energy?

5. Thermoregulation
The conditions outside your body are constantly changing.
One minute they can be hot, the next cold.
Despite these changes, your body must be kept at a constant temperature of…
37oC
The body needs to remain at 37oC is because this is the temperature at which our enzymes work most effectively.

6. Sensing body temperature
Body temperature is controlled by a region of the brain.
As blood flows around the body,
it passes through the thermoregulatory centre in the brain.
The brain senses body temperature by sensing the temperature of the blood.
rest of the body
Once the brain knows what the body temperature is, it can act to keep it steady.
How does the body react to hot and cold temperatures?

7. Temperature and enzymes
Enzymes are temperature-sensitive chemicals that control many of the chemical reactions in the body.
How are enzymes are affected when body temperature changes?
hotter
colder
37oC
Enzymes work slowly and the body is suffering.
Enzymes work most effectively and body is fine.
Enzymes are heat-damaged and body can become ill.

8. Increasing heat loss from the skin
When blood flows to the surface of the skin, it passes near the air surrounding the body.
This air is much cooler than the temperature of the blood.
heat
blood
skin
air
The heat within the blood escapes to the cool air.
You also lose water and sodium chloride when you sweat.
This causes body temperature to drop and you feel cooler.

9. chloride enzymes glucose kidneys temperature
Plenary
Name______________ Class___________ Date __________
Your body tries to keep a steady internal _______________
of 37 °C. This is the temperature at which _______________ work best. _______________ is a source of energy for cells.
The pancreas monitors the level of glucose in the blood. Your _______________ control the amount of water in your blood.
They are controlled by ADH (anti-diuretic hormone). Salt contains sodium and chloride ions. They are needed to help your body work properly. Levels of sodium and _______________ ions are controlled by the kidneys.
chloride enzymes glucose kidneys temperature

10. by the end of the lesson you will be able to
Learning objectives:
by the end of the lesson you will be able to
Explain the processes that take place in the body to maintain a constant temperature.
Explain the importance of keeping temperature at 37oC to allow the enzymes in the body to achieve there optimum rate of reaction.
Describe how water and ions are lost through the skin when sweating.

11. The
Internal
Environment in detail

12. Learning objectives: by the end of the lesson you will be able to:
explain that blood sugar levels provides cells with energy.
explain how the body regulates blood sugar levels through negative feedback.
understand that negative feedback is part of homeostasis and helps the body maintain its internal environment.
explain what happens if the body fails to maintain blood sugar levels.

13. Starter
Which body system?

14. Negative feedback
Some hormones affect only one target organ, but most affect more than one.
When the hormone has had the desired effect, further production of the hormone needs to be controlled.
Hormone production is controlled by a process called negative feedback.
The regulation of blood glucose level is an example of negative feedback.

15. Negative feedback – blood glucose
Which of these parts of the body are involved in the negative feedback process that regulates blood glucose?
The brain, the pancreas and the liver are all involved in regulating blood sugar.

16. Negative feedback – high blood glucose
The brain detects the level of glucose in the blood.
When the level of blood glucose increases above normal, what hormone does the pancreas release?
increased blood glucose

17. Negative feedback – high blood glucose
The pancreas is stimulated to release insulin.
What effect does this have?
The insulin stimulates the liver to take glucose from the blood and convert into glycogen, which is stored in the liver.
increased blood glucose
insulin

18. Negative feedback – high blood glucose
The level of glucose in the blood decreases, causing the pancreas to stop producing insulin.
What would happen if the pancreas kept on producing insulin?
insulin
increased blood glucose
blood glucose
returns to normal

19. Negative feedback – low blood glucose
Negative feedback also occurs when the blood glucose level decreases below normal.
This time the brain detects decreased blood glucose and so the pancreas is stimulated to release which hormone?
decreased blood glucose

20. Negative feedback – low blood glucose
The pancreas produces the hormone glucagon.
Glucagon stimulates the liver to convert glycogen back to glucose and release this glucose into the bloodstream.
glucagon
decreased blood glucose

21. Negative feedback – low blood glucose
The level of glucose in the blood increases, causing the pancreas to stop producing glucagon.
What would happen if the pancreas kept on producing glucagon?
glucagon
decreased blood glucose
blood glucose
returns to normal

22. Blood glucose activity

23. When hormones go wrong – diabetes
What happens if the pancreas is unable to produce the hormone insulin?
Lack of insulin production means that the blood glucose level is unregulated and causes
the condition known as “sugar diabetes”.
After a person with diabetes has eaten, their blood glucose level increases. What happens to this glucose?
The absence of insulin means that glucose is not converted to glycogen and stored in the liver, so the blood of a
diabetic contains extra glucose.

24. When hormones go wrong – diabetes
Glucose is essential for
the body, so why is excess glucose a danger for people with diabetes?
The ability of the kidneys to
absorb glucose is also exceeded, so the excess is excreted in urine.
When the glucose is used up, coma and convulsions may occur. So how is diabetes controlled?
Regular insulin injections and a careful diet can control the condition.

25. Multiple-choice quiz
Multiple-choice quiz

26. Learning objectives: by the end of the lesson you will be able to:
explain that blood sugar levels provides cells with energy.
explain how the body regulates blood sugar levels through negative feedback.
understand that negative feedback is part of homeostasis and helps the body maintain its internal environment.
explain what happens if the body fails to maintain blood sugar levels.